Reproduction method



Dec. 12, c BRYNKO REPRODUCTION METHOD F'iled Sept. 3, 1965 INVENTOR. CARL BRYNKO BY M ATTORNEYS United States Patent O 3,357,354 REPRODUCTION METHOD Carl Brynko, West Webster, N.Y., assignor to Xerox Corporation, Rochester, N.Y., a corporation of New York Filed Sept. 3, 1965, Ser. No. 484,806 6 Claims. (101-472) ABSTRACT OF THE DISCLOSURE An imaging process is described in which a copy sheet having fixed on the surface thereof a layer of capsules containing a solvent is pressed against an image with sufficient pressure to rupture the capsules. The solvent dissolves part of the image-forming material and transfers it to the receiving sheet. Thus, an image is formed on the receiving sheet which is a reversal of the original. The thus-formed image may be retransferred either by pressing the imaged receiving sheet against a third sheet immediately after stripping from the original or by pressing the imaged receiving sheet against a second receiving sheet having a similar layer of encapsulated solvent.

This invention relates in general to imaging systems and, more specifically, to an improved method for copying original images.

Many widely varying image copying processes are in commercial use today. These include both wet and dry processes and processes which are capable of producing a single copy or multiple copies from a single original. Some processes require a master and some do not. While each particular process has its own advantages in quality, economy, or simplicity each also has disadvantages which renders it less than ideal for all copying requirements.

One Well-known copying process is the diffusion transfer process which uses two different sheets of chemically treated paper. One is a negative sheet which is coated with a gelatin emulsion containing a silver halide and other materials and which is sensitive to light. The other sheet is the positive which is coated with a silver nucleating agent and which is not sensitive to light. The original document is placed face down against the gelatin layer of the negative sheet and is exposed to visible light. The light passes through the negative, strikes the original and is reflected back from the non-imaged areas of the original onto the negative sheet. In these areas a silver halide latent image is formed. After exposure, the negative sheet is separated from the original and placed against the positive paper. The two are placed in a developer solution which develops the silver halide in the latent image areas of the negative. In non-imaged areas, a silver halide complex is formed which is transferred by diffusion to the positive sheet pressed against it. When this complex reaches the nucleating agent in the positive sheet, a colored image is formed. The two sheets are separated and allowed to dry. This produces a black-and-white copy on the colored sheet corresponding to the original. As can be seen from the above description, this process requires several sheets coated with complex materials, several handling steps, and requires a liquid developer. Ordinarily, only a single positive copy can be made from a single negative.

Another widely used copying process is the gelatin transfer process. This process uses a light sensitive sheet called a matrix, which consists of paper coated with unhardened gelatin and several color forming chemicals. The matrix is exposed to the original image by reflex. The matrix is then placed in a developer solution which hardens the gelatin in light exposed areas and forms a color throughout the matrix. The matrix is removed from the developer, squeezed against copy paper and then 3,357,354 Patented Dec. 12, 1967 stripped therefrom. A thin layer of the soft, swollen gelatin is transferred to it in image configuration. It is possible for a skilled operator to make up to ten copies from a single matrix. However, these images are often of low density and tend to fade with time. Also the process is somewhat complex and time consuming and requires the use of liquid developers.

The diazo process is widely used in copying engineering and architectural drawing. In this process, the original document, which must be on a transparent or translucent sheet, is placed face up over paper sensitized with a diazonium compound. The paper is exposed to ultraviolet light passing through the original, after which it is treat ed with ammonia. An azo dye is thus formed in image areas. While this process does not require liquid developers, the ammonia gas used is often objectionable. Although this is the cheapest of the widely used copying methods, it is severely limited by the requirement that the original image be on a transparent or translucent base.

Several thermographic imaging processes are known. Here, copies are made on treated paper which contains compounds that form colored substances when heated. The copy sheet is placed over the original and exposed to infrared radiation. The infrared is not absorbed by the treated paper and, therefore, does not affect it directly. However, where the infrared strikes printed areas of the original, it is absorbed and heat is generated. This heat causes a chemical reaction in corresponding areas of the copy sheet forming a colored image. This process is capable of producing images of generally satisfactory quality, inexpensively and without liquid developers. The images, however, often suffer from a lack of sharpness and may fade with exposure to light or heat. Also, this process is unable to copy colored inks which do not absorb infrared, such as those used in many ball point pens.

The most recently developed widely used copying methods are the electrophotographic processes as exemplified by that described by Carlson in US. Patent 2,297,691. In this process, a base sheet of relatively low electrical resistance such as metal, paper, etc. having a photoconductive insulating surface coated thereon, is electrostatically charged in the dark. The charged coating is then exposed to a light image. The charges leak ofr" rapidly to the base sheet in proportion to the intensity of the light to which any given area is exposed, the charge being substantially retained in the non-exposed areas, forming a latent electrostatic image. After exposure, the coating is contacted with electroscopic marking particles in the dark. These particles adhere to the areas where the electrostatic charge remains, forming a powder image corresponding to the electrostatic image. Where the base sheet is relatively inexpensive, such as paper, the image may be fixed directly to the plate as by heat or solvent fusing. Alternatively, the powder image may be transferred to a sheet of material, such as paper, and fixed thereon. This process is capable of producing images of especially high quality. These processes can rapidly produce many copies of a single original without the use of liquid developers. However, the process is relatively complex mechanically requiring high voltage power supplies, powder developer handling apparatus, and thermofusing means to fix the image.

Thus, it can be seen that there is a continuing need for improved methods of copying original images.

It is, therefore, an object of this invention to provide an image copying process which overcomes the above noted deficiencies.

It is another object of this invention to provide a simple, inexpensive, dry method of copying original images.

Is is another object of this invention to provide a copying process which is capable of producing multiple copies from a single original.

It is still another object of this invention to provide a copying process capable of copying any image which consists of soluble image material.

The foregoing objects and others are accomplished in accordance with this invention, fundamentally, by providing a copying process utilizing a receiving sheet, the surface of which is coated with a uniform layer of small capsules containing a solvent for the original image material. This sheet is placed in contact with the original image and pressed thereagainst so as to rupture the solvent containing capsules. The released solvent dissolves a portion of the original image material, causing transfer of that portion to the receiving sheet so that a reverse image is produced on the receiving sheet when it is stripped from the original. This receiving sheet may then be the final copy where either a reverse image is acceptable or where the original image was a reversal and, therefore, the copy is right reading. Alternatively, the transfer sheet may be pressed against a third sheet of absorbent material, such as paper, immediately after the receiving sheet is stripped from the original and before the solvent has evaporated. This will transfer a portion of the original image material to the third sheet, producing a copy conforming in all respects to the original. Where suflicient material was transferred to the receiving sheet, a plurality of third sheets may be used to produce a plurality of duplicate, copies. Since only a portion of the image material is removed from the original, a plurality of copies may be made from the original.

Any original image may be copied by this process in which the original image is formed from a dissolvable material. The solvent encapsulated on the surface of the receiving sheet ischosen so as to dissolve the image material of the originals to be copied. Typical image materials which may be copied by this process include conventional printing ink images such as are found in newspapers and magazines, and conventional electrophotographic images which comprise a resin and colorant. In general, a solvent which is suitable for dissolving a portion of a resinous electrophotographic image is equally suitable for dissolving a portion of a printing ink image. Only a very small amount of solvent is necessary in the capsules on the receiving sheet. This copying technique is unusually elfective even with relatively small controlled amounts of solvents, in the capsules because the solvent is released at the interface between the original image and the receiving sheet. Therefore, the solvent first softens that side of the image material adjacent the receiving sheet causing it to wet this sheet almost immediately upon solvent release and. does not require diffusion of the solvent through the top side of the image material before the image material can wet the underlying receiving sheet. In fact, it has been found with a system of this invention, the amount of solvent required in the capsules is so small that the fixing process may be carried out in an open room without benefit of a vapor container while still not releasing sufficient solvent to the atmosphere to be even noticeable, let alone offensive or toxic, to human operators.

The features and advantages of the present invention will become further apparent upon consideration of the following detailed disclosure of exemplary embodiments of the invention, especially when taken in conjunction with the accompanying drawings wherein:

FIG. 1 schematically shows the transfer of a portion of an original image to a copy sheet; and

FIG. 2 schematically shows the retransfer of the image material transferred in FIG. 1 to a third sheet, producing a right-reading image.

Referring now to FIG. 1, there is seen a sheet 1 on which is present an original image 2. This image 2 may comprise any dissolvable material. Typically, this image may comprise a thermoplastic resin and a colorant deposited, for example, by the electrophotographic process described in US. Patent 2,297,691. Also, the image may comprise the conventional oil base printing inks such as used in conventional newspapers and magazine printing. Typical printing ink compositions are described in Carlton Ellis book Printing Inks, Reinhold Publishing Co. (1940). Any other suitable image material may be used as desired. Pressed tightly against sheet 1 by pressure rollers 3 and 4 is a receiving sheet 5. This receiving sheet 5 comprises a substrate 6-which may be paper, metal, plastic or any other suitable material. Coated on the surface of substrate 6 is a layer 7 comprising a multiplicity of small capsules. Thesecapsules may be coated onto the substrate by the methods described in US. Patents 2,730,456 and 2,712,507, for example. The minute capsules in layer 7 comprise droplets of a solvent capable of dissolving the original image material2 encapsulated with a rupturable resin material. These capsules may be adhesively bonded. into layer 7 against substrate 6. In some instances, where the capsules are applied in a somewhat tacky condition they will bond together and to substrate 6 without requiring additional adhesive. As is further discussed below, the solvent may be any composition which is a solvent for the image material and the encapsulating resin may be any rupturable resin which is resistant to the encapsulated solvent. As sheet 1 carrying the original image and receiving sheet 5 pass together between pressure rollers 3 and 4, the minute capsules are ruptured atthe roller nip releasing the solvent into contact with the original image carrying surface. The solvent dissolves a portion of the original image which portion transfers to the surface of the receiving sheet 5. As shown in FIG. 1, when sheets 1 and 5 are separated an image is seen on receiving sheet 5 which is the reverse of the original image. Where the reversal image is acceptable, or where the original image had been formed as a reversal image, the residual solvent on receiving sheet 5 may be allowed to evaporate and the copy may then be handled without fear of injury to the image.

Where the reversal image formed on receiving sheet 5 is not suitable for the intended use, a right-reading copy of this image may be prepared as by the process schematically shown in FIG. 2. Immediately after the image is formed on receiving sheet 5, before thesolvent has evaporated, it is passed again through pressure rolls 3 and 4, this time in contact with a transfer sheet 8 which may be another composite sheet. In this process,-the transfer sheet would carry solvent containing capsules on its surface which would rupture as sheets 8 and 5 pass through the nip of rollers 3 and 4. A portion of the image on sheet 5 would be transferred to sheet 8 in a mannner identical to that shown in above described FIG. 1. A plurality of duplicate copies of the image on sheet 5 could be made by this method, limited only by the density of the image on sheet 5. These secondary copies would be right-reading and would conform to the original image on sheet 1. Alternatively, where the image on sheet 5 has not been allowed to dry, duplicate copies may be made on transfer sheet 8 in the manner shown in FIG. 2 by utilizing as this sheet a sheet of absorbent material, such as paper. Since the image or the receiving sheet is still in a partially dissolved state, a portion of the image is transferred to transfer sheet 8, as sheets 6 and 5 pass through the nip of rollers 3 and 4, producing a rightreading image corresponding to the original image on sheet 1. Receiving sheet 5 may be passed through rollers 3 and 4 in contact with additional absorbent sheets producing additional duplicate copies so long as the solvent has not evaporated from the image on sheet 5. For this purpose, a high boiling point solvent, such as xylene, should preferably be used.

The coating of encapsulated solvent may be formed by any conventional method. Suitable techniques for forming encapsulated solvents and coating them on paper substrates are disclosed in US. Patents 2,800,457 and 2,800,-

458 to Green and 2,969,330, 3,116,206 and 2,969,331 to Brynko. The Green patents describe encapsulation of the solvents in a hydrophilic colloid material and generally may be employed to encapsulate any water immiscible solvent (which is less than about 1 percent soluble in water) including, for example, kerosene, xylene, chlorinated diphenyls, such as trichlorodiphenyl and the like. The Brynko patents describe encapsulation of these solvents in a cross-linked synthetic polymer such as crosslinked pol styrene and zein. Because of this fact, these capsules may retain some solvents which would tend to attack the hydrophilic colloid capsule shell described in the Green patents. Techniques for encapsulating solvents with condensation polymers such as ureaformaldehyde resins are also known in the art and may be employed in connection with this invention. The particular size of capsules used is not critical. Capsule sizes from about 2 to about 100 microns would be useful. However, capsules of about 2 to 5 microns would require rather large pressures for rupturing, and particles of over 80 microns diameter might tend to rupture under normal handling under moderate pressure. Optimum results are obtained with capsule size in the range of 30 to 70 microns. The only requirement which the solvent must meet is that it readily dissolve the original image material. It should have a boiling point above 40 C. to prevent loss during prolonged storage. Any suitable solvent material may be used as desired. Typical solvents include: toluene, xylene, methylene chloride, kerosene, chlorinated diphenyls and mixtures thereof. Where the original image to be copied comprises a printing ink image or a colored resin image such as results from conventional electrophotographic imaging processes, the preferred solvents are xylene and toluene. These solvents have been found to produce images of the highest density and the greatest number of copies of a single original image.

The capsulses which contain the solvent may comprise any material which is resistant to attack from the solvent contained therein and which are rupturable by the application of pressure. Typical monomers Which may be polymerized in the form of capsules by the processes described in the above-mentioned Green and Brynko patents include ethylacrylate, methylacrylate, methylmethacrylate, ethylmethacrylate, vinyl acetate, styrene and mixtures thereof. These monomers, when formed into capsules by the methods described in the above cited patents, form tough, highly cross-linked polymers, very resistant to attack by the usual solvents. If desired, dualwall capsules may be used, of the sort described in US. Patent 2,969,331.

The following examples further specifically define the present invention with respect to copying processes utilizing encapsulated solvent coated transfer sheets. Parts and percentages are by weight unless otherwise indicated. The examples below are intended to illustrate various preferred embodiments of the processes of the present invention.

Example I A sheet of ordinary bond paper is coated with a uniform layer of polystyrene capsules containing benzene by the process described in [1.5. Patent 2,969,330. The individual capsules have an average diameter of about 50 microns. The coated surface is placed in contact with a sheet of newsprint which had been conventionally printed. The two sheets are then passed between a pair of 3" diameter stainless pressure rolls which apply a pressure of about 100 lbs. per lineal inch to the sheets. The two sheets are immediately separated after they pass through the nip between the rolls. A reversal image of good density is observed on the coated sheet. This coated sheet is placed face down on another sheet of bond paper and the pair is passed through the same pressure rolls. The two sheets are separated after they pass through the nip between the rolls. An image of good quality and satisfactory density corresponding to the original is observed on the final copy sheet. Five additional capsulecoated sheets are sequentially passed between the rollers in contact with the same sheet of printed newsprint. A duplicate image is seen on each, with some fall-oif in image density on the later copies. As a control, a sheet of ordinary uncoated bond paper is laced in contact with another sheet of newsprint and the composite is passed through the roller nip. Upon separation of the two sheets, a very faint ink image is seen on the bond paper; apparently due to transfer from incompletely dried printing ink on the newsprint.

Example 11 A capsule coated sheet of bond paper is prepared as in Example I above. An original image comprising bond paper having thereon an image made up of a mixture of 10 percent carbon black, 25 percent polybutylmethacrylate, and 65 percent of a blend of polymerized styrenes. The original image is made by the xerographic process as described in US. Patent 2,297,691. The capsule coated surface of the receiving sheet is placed in face-to-face contact with the original image sheet. The composite is passed between a pair of 3 inch diameter stainless steel rollers which exert a pressure of about lbs. per lineal inch on the sheets. Immediately after the composite sheets pass between the rollers, they are separated and a reversal image of excellent quality is observed on the transfer sheet. The transfer sheet is immediately placed in contact with a sheet of ordinary bond paper and the pair is passed between the nip between the rollers again. The sheets are separated after passing through the rollers and an image of good quality, but lower density is observed on the bond paper. This image corresponds to the original. Ten additional capsule coated sheets are sequentially passed through the rollers in contact with the same original image. An image of excellent quality is seen on each sheet, with very little decrease in quality from the first to last copy. As a control, a sheet of ordinary bond paper is placed in contact with another sheet having a xerographic image thereon. The pair of sheets is passed through the nip between the pressure rollers. The sheets are then separated and no image transfer is observed to the sheet of bond paper.

Example III A capsule coated sheet of bond paper is prepared as in Example I above. In this instance, the capsule comprises polymethylmethacrylate and the solvent is xylene. An original image is prepared xerographically, as described in Example II above. The capsule-coated side of the receiving sheet is placed in face-to-face contact with the original image and the composite is slowly passed between a pair of 3 inch diameter stainless steel pressure rolls which exert a pressure of about 100 pounds per lineal inch on the sheets. Upon separation of the sheets an excellent, reversal, image is observed on the receiving sheet. The residual solvent is allowed to evaporate, leaving a tough, hardenable image. Five additional capsule coated sheets are then sequentially placed in face-to-face contact with the image on the receiving sheet and are passed rapidly between the same rollers. Images of excellent quality, right-reading, conforming to the original image are produced, with very little fall-off in quality from first copy to last.

Although specific components and proportions have been stated in the above description of preferred embodiments of the materials utilized in the process of this invention, other suitable materials as listed above may be used with similar results. In addition, other materials may be added to the solvent, to the encapsulating resin, and to the various transfer sheets to synergize, enhance, or otherwise modify their respective properties. For example, the capsule forming resins may be plasticized as desired or the final transfer sheets could have various surfactants added thereto to aid in image transfer.

Other modifications and ramifications of the present invention will occur to those skilled in the art upon a reading of this disclosure. These are intended to be included within the scope of this invention.

What is claimed is:

1. An imaging process comprising the steps of:

(1) providing a receiving sheet. having fixed on the surface thereof a substantially uniform layer of capsules containing a solvent;

(2) bringing said receiving sheet into contact with an original sheet having an image thereon, said image comprising a material at least partially soluble in said solvent;

(3) pressing said capsule bearing face of said receiving sheet against said image so as to rupture said capsules, releasing said solvent which at least partially dissolves said image material whereby a portion of said image material is transferred to said receiving sheet; and,

(4) stripping said receiving sheet from said original sheet.

2. The process of claim 1 wherein the steps 14 are repeated with additional receiving sheets and a single original sheet at least five times.

3. The process of claim 1 wherein the receiving sheet is pressed against a third sheet immediately after it is stripped from the original and before the released solvent has evaporated, whereby at least part of the imaging material transferred to the receiving sheet is retransferred to the third sheet.

4. The process of claim 1 wherein said original image material comprises a resin and a colorant.

5. The process of claim 1 wherein the steps 1-4 are repeated with the imaged receiving sheet in place of the original sheet, whereby a portion of the transferred image is re-transferred to another sheet.

6. The process of claim 1 wherein said capsules comprise shells surrounding droplets of a solvent selected from p the group consisting of Xylene and toluene.

References Cited DAVID KLEIN, Primary Exa/m'ner.

ROBERT E. PULFREY, Examiner.

I. A BELL, Assistant Examiner. 

1. AN IMAGING PROCESS COMPRISING THE STEPS OF: (1) PROVIDING A RECEIVING SHEET HAVING FIXED ON THE SURFACE THEREOF A SUBSTANTIALLY UNIFORM LAYER OF CAPSULES CONTAINING A SOLVENT; (2) BRINGING SAID RECEIVING SHEET INTO CONTACT WITH AN ORIGINAL SHEET HAVING A IMAGE THEREON, SAID IMAGE COMPRISING A MATERIAL AT LEAST PARTIALLY SOLUBLE IN SAID SOLVENT; (3) PRESSING SAID CAPSULE BEARING FACE OF SAID RECEIVING SHEET AGAINST SAID IMAGE SO AS TO RUPTURE SAID CAPSULES, RELEASING SAID SOLVENT WHICH AT LEAST PARTIALLY DISSOLVES SAID IMAGE MATERIAL WHEREBY A PORTION OF SAID IMAGE MATERIAL IS TRANSFERRED TO SAID RERECEIVING SHEET; AND, (4) STRIPPING SAID RECEIVING SHEET FROM SAID ORIGINAL SHEET. 